Astronomy Picture of the Day

   [1]Discover the cosmos! Each day a different image or photograph of our
      fascinating universe is featured, along with a brief explanation
                    written by a professional astronomer.

                               2021 August 29
       [2]The picture is an illustration of the orbits of potentially
   hazardous asteroids that may, one day in the distant future, strike the
      Earth. Please see the explanation for more detailed information.

                  Orbits of Potentially Hazardous Asteroids
                    Image Credit: [3]NASA, [4]JPL-Caltech

   Explanation: Are asteroids dangerous? Some are, but the likelihood of a
   dangerous asteroid striking the Earth during any given year is low.
   Because some past mass [5]extinction events have been linked to
   asteroid impacts, however, humanity has made it a priority to find and
   catalog those [6]asteroids that may one day affect [7]life on Earth.
   [8]Pictured here are the orbits of the over 1,000 known [9]Potentially
   Hazardous Asteroids (PHAs). These documented tumbling [10]boulders of
   rock and ice are over 140 meters across and will pass within 7.5
   million kilometers of Earth -- about 20 times the distance to the Moon.
   Although none of them will [11]strike the Earth in the next 100 years
   -- [12]not all PHAs have been discovered, and past 100 years, many
   orbits become hard to predict. Were an asteroid of this size to
   [13]impact the Earth, it could raise [14]dangerous tsunamis, for
   example. To investigate Earth-saving strategies, NASA's [15]Double
   Asteroid Redirection Test ([16]DART) is planned for launch later this
   year. Of course rocks and ice bits of much smaller size [17]strike the
   Earth every day, usually pose no danger, and sometimes creating
   [18]memorable fireball and [19]meteor displays.

                      Tomorrow's picture: ice sky fire
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    Authors & editors: [31]Robert Nemiroff ([32]MTU) & [33]Jerry Bonnell
                                 ([34]UMCP)
          NASA Official: Phillip Newman [35]Specific rights apply.
              [36]NASA Web Privacy Policy and Important Notices
                A service of: [37]ASD at [38]NASA / [39]GSFC
                           & [40]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2108/phas_jpl_3254.jpg
   3. https://www.nasa.gov/
   4. https://www.jpl.nasa.gov/
   5. https://en.wikipedia.org/wiki/Cretaceous–Paleogene_extinction_event
   6. http://www.jpl.nasa.gov/asteroidwatch/
   7. https://apod.nasa.gov/apod/ap170326.html
   8. https://photojournal.jpl.nasa.gov/catalog/PIA17041
   9. https://en.wikipedia.org/wiki/Potentially_hazardous_object
  10. https://commons.wikimedia.org/wiki/File:Balanced_Rock.jpg
  11. https://www.youtube.com/watch?v=_COcHHvte-0
  12. https://www.nasa.gov/mission_pages/WISE/multimedia/gallery/neowise/pia14734.html
  13. https://en.wikipedia.org/wiki/Impact_event
  14. http://www.youtube.com/watch?v=w3AdFjklR50
  15. https://www.nasa.gov/planetarydefense/dart
  16. https://en.wikipedia.org/wiki/Double_Asteroid_Redirection_Test
  17. https://apod.nasa.gov/apod/ap210131.html
  18. https://apod.nasa.gov/apod/ap130218.html
  19. https://apod.nasa.gov/apod/ap121119.html
  20. https://apod.nasa.gov/apod/ap210828.html
  21. https://apod.nasa.gov/apod/archivepix.html
  22. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  23. https://apod.nasa.gov/apod/lib/aptree.html
  24. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  25. https://apod.nasa.gov/apod/calendar/allyears.html
  26. https://apod.nasa.gov/apod.rss
  27. https://apod.nasa.gov/apod/lib/edlinks.html
  28. https://apod.nasa.gov/apod/lib/about_apod.html
  29. http://asterisk.apod.com/discuss_apod.php?date=210829
  30. https://apod.nasa.gov/apod/ap210830.html
  31. http://www.phy.mtu.edu/faculty/Nemiroff.html
  32. http://www.phy.mtu.edu/
  33. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  34. http://www.astro.umd.edu/
  35. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  36. https://www.nasa.gov/about/highlights/HP_Privacy.html
  37. https://astrophysics.gsfc.nasa.gov/
  38. https://www.nasa.gov/
  39. https://www.nasa.gov/centers/goddard/
  40. http://www.mtu.edu/